exo·​sphere | \ ˈek-sō-ˌsfir How to pronounce exosphere (audio) \

Definition of exosphere

: the outer fringe region of the atmosphere of the earth or a celestial body (such as a planet)

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Other Words from exosphere

exospheric \ ˌek-​sō-​ˈsfir-​ik How to pronounce exospheric (audio) , -​ˈsfer-​ How to pronounce exospheric (audio) \ adjective

Examples of exosphere in a Sentence

Recent Examples on the Web The mysterious moon has a very, very thin atmosphere, called an exosphere, that’s rich in carbon dioxide, and trace amounts of oxygen and nitrogen. Jennifer Leman, Popular Mechanics, "Every Moon in Our Solar System, Ranked," 7 Apr. 2020 Mercury has what’s called an exosphere made from solar-wind propelled oxygen, sodium, hydrogen, helium, and potassium atoms that have bounced off the planet's surface. Jennifer Leman, Popular Mechanics, "Small Yet Mighty Mercury Still Holds Many Mysteries," 9 Nov. 2019 The problem is that if there really are 1,000 ions per cubic centimeter, the ionization of gas in the lunar exosphere can’t account for such a high concentration—there just isn’t enough gas. Daniel Oberhaus, WIRED, "Lunar Mysteries That Science Still Needs to Solve," 16 July 2019 In the 1970s two Soviet lunar orbiters discovered that ions also existed in the moon’s ultra-thin exosphere, and scientists have been trying to explain this observation ever since. Daniel Oberhaus, WIRED, "Lunar Mysteries That Science Still Needs to Solve," 16 July 2019 Instead scientists refer to its extremely thin covering of oxygen, hydrogen, sodium, helium, and potassium as an exosphere. National Geographic, "The solar system, explained," 27 Mar. 2019 Because nitrogen is a volatile chemical, some of it sublimates and gives Pluto a tenuous atmosphere still thick enough to be more than an exosphere. John Wenz, Popular Mechanics, "Here's What We Know About Pluto So Far," 17 July 2015 The spacecraft has two spectrometers that will be analyzing the exosphere. Joe Pappalardo, Popular Mechanics, "4 More Hurdles the LADEE Moon Mission Must Clear," 9 Sep. 2013 Team Unsullied seemed poised for a predictable victory, when suddenly — his square jawline visible from the exosphere — along came dependable ol’ Jaime Lannister, sacking Highgarden and laying waste to Dany’s plans at the last minute. Anna Silman, The Cut, "I’m Rooting for the Lannisters," 4 Aug. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'exosphere.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of exosphere

1949, in the meaning defined above

History and Etymology for exosphere

exo- + -sphere

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Time Traveler for exosphere

Time Traveler

The first known use of exosphere was in 1949

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Statistics for exosphere

Cite this Entry

“Exosphere.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/exosphere. Accessed 29 Sep. 2020.

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More Definitions for exosphere


exo·​sphere | \ ˈek-sō-ˌsfir How to pronounce exosphere (audio) \

Kids Definition of exosphere

: the outermost region of the atmosphere

More from Merriam-Webster on exosphere

Britannica.com: Encyclopedia article about exosphere

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